feat: add display UI with splash screen, dashboard, and RSSI sparkline

Implement full SSD1306 OLED display support:
- Splash screen on boot (1.5s) with project name, version, board
- Dashboard showing radio state, config, counters, RSSI/SNR
- RSSI history sparkline (64-sample ring buffer, 2px-wide bars)
- DisplayOn/DisplayOff host commands routed via dedicated channel
- Pure render functions against generic DrawTarget (no hardware coupling)
- Display on/off control bypasses radio task entirely

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/object/tests/read/elf.rs

@@ -0,0 +1,47 @@
+#[cfg(feature = "std")]
+use std::path::{Path, PathBuf};
+
+#[cfg(feature = "std")]
+fn get_buildid(path: &Path) -> Result<Option<Vec<u8>>, object::read::Error> {
+    use object::Object;
+    let file = std::fs::File::open(path).unwrap();
+    let reader = object::read::ReadCache::new(file);
+    let object = object::read::File::parse(&reader)?;
+    object
+        .build_id()
+        .map(|option| option.map(ToOwned::to_owned))
+}
+
+#[cfg(feature = "std")]
+#[test]
+/// Regression test: used to attempt to allocate 5644418395173552131 bytes
+fn get_buildid_bad_elf() {
+    let path: PathBuf = [
+        "testfiles",
+        "elf",
+        "yara-fuzzing",
+        "crash-7dc27920ae1cb85333e7f2735a45014488134673",
+    ]
+    .iter()
+    .collect();
+    let _ = get_buildid(&path);
+}
+
+#[cfg(feature = "std")]
+#[test]
+fn get_buildid_less_bad_elf() {
+    let path: PathBuf = [
+        "testfiles",
+        "elf",
+        "yara-fuzzing",
+        "crash-f1fd008da535b110853885221ebfaac3f262a1c1e280f10929f7b353c44996c8",
+    ]
+    .iter()
+    .collect();
+    let buildid = get_buildid(&path).unwrap().unwrap();
+    // ground truth obtained from GNU binutils's readelf
+    assert_eq!(
+        buildid,
+        b"\xf9\xc0\xc6\x05\xd3\x76\xbb\xa5\x7e\x02\xf5\x74\x50\x9d\x16\xcc\xe9\x9c\x1b\xf1"
+    );
+}